1. Field of the Invention
This invention relates to an AC type plasma display panel, referred to hereinafter as a PDP, of matrix formation, particularly to a PDP having a screen which is divided into a plurality of sub-screens.
2. Description of the Related Arts
A prior art surface discharge type PDP is hereinafter described with reference to FIG. 1 schematically illustrating a plan view of the electrode configuration, and FIG. 2 schematically illustrating a decomposition perspective view of the internal structure.
Prior art PDP 80 includes a plurality of electrode pairs 12j of first and second sustain electrodes Xj & Yj in parallel with each other and extending straight, both of which may be called main electrodes, and a plurality of address electrodes Aj in straight and orthogonal to first and second sustain electrodes Xj & Yj. Each electrode pair 12j corresponds to a single line of the matrix formation, and each address electrode Aj corresponds to a single row. That is, an area E1 where the sustain electrodes and the address electrodes intersect each other is a displaying area, referred to hereinafter as a screen. In the periphery of the screen is provided a non-lighting area E2 of a predetermined width in order to be free from an effect of a gas degased from sealant to seal the two glass substrates 11j and 21j.
As shown in FIG. 2, a prior art PDP 80 is constituted with a front glass substrate 11j, first and second sustain electrodes Xj & Yj, a dielectric layer 17j for an AC drive, a protection layer 18j, a back glass substrate 21j, address electrodes Aj, separator walls 29j and fluorescent material layers 28j for a full-color display. A discharge space 30j therein is divided into each subpixel EU along a line direction, that is, a direction along which sustain electrodes Xj & Yj extend, by separator wall 29j, which also determines a gap between the substrates.
First and second sustain electrodes Xj & Yj are arranged on an inner surface of back glass substrate 21j, and each of which is formed of a wide transparent electrically conductive film 41j and a metal film 42j thereon for securing a good electrical conductivity. Transparent electrically conductive film 41j is patterned belt-like wider than metal film 42j so that a surface discharge may expand.
Fluorescent material layer 28j is coated between each separator wall 29j on back glass substrate 21j in order to reduce an ion bombardment, and emits a light by a local excitation of ultraviolet rays generated in the surface discharge. Among the visible radiations emitted from the surface of fluorescent layer 28j, i.e. the surface to face the discharge space, the light which can penetrate through glass substrate 11j becomes a display light.
Pixel, i.e. picture element, EG of the screen matrix includes three sub-pixels EU which line up along the line direction, where the lighting colors of the three sub-pixels EU are mutually different as denoted with R, G and B, so that each color to be displayed of a single pixel is determined by the combination of the basic R, G and B. The pattern arrangement of separator walls 29j is so-called a stripe pattern, where the part which corresponds to each row in discharge space 30 extends in the row direction continuously to cross over all the lines. The emitting color of sub-pixels EU in each row is identical.
Second sustain electrode Yj of the electrode pair 12j and address electrode Aj are used for selecting, i.e. addressing, a pixel EU to light or not to light. That is, a screen scanning is performed sequentially line by line by applying a scan pulse onto sequential one of n second sustain electrodes Yj, where n indicates the quantity of the lines, and a predetermined electrically charged state is formed in the selected cell of each row by an opposing discharge, i.e. an address discharge, generated between the second sustain electrode Yj and an address electrode Aj selected in accordance with the contents to be displayed. After the addressing operation is thus performed, upon an application of the sustain pulses of a predetermined peak value alternately onto first and second sustain electrodes Xj & Yj a surface discharge, i.e. a sustain discharge, takes place in the cell in which wall charges of a predetermined amount ;remaining at the end of the addressing operation.
In performing the addressing operation according to the above-described line-scanning, if the quantity of the lines are increased so as to meet a requirement to enhance the screen size or to accomplish a higher resolution, the period required for the addressing operation becomes longer. However, a single frame, that is a period for displaying a single picture, is unalterable. Accordingly, the longer the addressing period becomes, the shorter the time length allocatable to the sustain period becomes, resulting in inadequate brightness of the display. Moreover, the gradation display by dividing the frame become difficult.
Therefore, it has been measured to divide screen E1 along the row direction, that is, along upper and lower direction of FIG. 1 into plural partial screens in each of which the addressing operation is concurrently performed. Then, address electrodes Aj are divided into each partial screen too. Dividing of the display screen into two partial screens allows the period required for the addressing operation to reduce to a half.
However, in dividing all the sustain electrode pairs simply into two partial screens, there is a problem in that an erroneous discharge may take place across the border line where the second sustain electrode Y of the first sub-screen E11 faces the first sustain electrodes of the next line of the next partial screen E12.
This problem is hereinafter described in detail with reference to FIGS. 3A and 3B. FIG. 3B schematically illustrates a cross-sectional view of the electrode structure cut along b--b of FIG. 3A. Display screen E1 is divided into two partial screens E11 and E12. In each of partial screens E11 and E12 are provided partial address electrodes A1j and A2j, respectively, symmetric with respect to the border line DL. However, in practically sealing the two glass substrates the symmetry may be somewhat deviated. Clearance Dj between two partial address electrodes A1j and A2j respectively of first and second partial screens E11 and E12 is chosen narrower than the electrode clearance d between two lines. This is in order to keep properly the positional relation between second sustain electrode Y and partial address electrode A, even in the case where the symmetry is deteriorated due to a miss-alignment of the facing two glass substrates during the sealing operation, that is, the end of first partial address electrode A1 can always cross over the last second sustain electrode Yn, so that an address discharge can certainly take place between first partial address electrode A1 and the last second sustain electrode Yn of the first partial screen.
However, in the case where addressing operation is performed concurrently for two partial screens E11 and E12, when addressing discharge is generated only in one of the partial screens there is generated a potential different between two partial address electrodes A1jn and A2jn. Accordingly, the narrower the clearance Dj is, the more likely an erroneous discharge, or an interference, generates between two partial address electrodes A1j and A2j or between a second sustain electrode Yjn and a second partial address electrode A2jn+1 of second partial screen.